Steel



Patented May 16, 1939 .PATENT 2,158,651 OFFICE STEEL Frederick. M.Becket,

New York, and Russell Franks, Niagara Falls, N. Y., assignors to ElectroMetallurgical Company, a corporation of West Virginia No Drawing.Application June 24, 1936, Serial N0. 87,006

7 Claims.

This invention relates to steels, and provides new and improved steelscharacterized by novel and commercially valuable properties.

We have discovered that the addition of co ,3 lumbium in amounts between0.02% and 1% to so-called plain carbon and certain low alloyed steelseffects a marked and surprising improvement in the properties of suchsteels. One important efiect of the columbium addition is to refine thegrain-size of the steel, and this grain refinement is retained andmaintained even at elevated temperatures up to and somewhat above thecritical range. Another eiiect, which is doubtless at least in part aresult of the grain refinement, is the improvement of the tensilestrength of many of the steels. Further, the impact strength isincreased, and this improvementis marked even atsubzero temperatures,There is also an increase in the resistance of the steels.

to rusting and hot oxidation. The deep-drawing and cold-rollingcharacteristics of the steels are improved. The hardenability of thesteels by heat treatment is somewhat decreased, and there islessdistortion of the steel when it is rapidly cooled from elevatedtemperatures. The ratio of yield point to maximum stress is increased,the increase depending upon the columbium and carbon contents of thesteels: the increase is greater in the steels having the lower carbonand columbium contents.

Steels included in our invention are: e

A. Plain carbon steels containing carbon in amounts not exceeding 1% andpreferably not exceeding 0.6%, silicon in amounts up to 1%, manganese inamounts up to 2%, and suitable amounts of columbium, the remainder iron.

B. Chromium steels containing carbon in amounts not exceeding 0.6% andpreferably not over 0.4%, 0.25% to less than 2% chromium, silicon inamounts up to 1%, manganese in amounts up to 2%, suitable amounts ofcolumbium, and the remainder iron.

C. Chromium-nickel steels containing, "in addition to the ingredients ofthe chromium steels, 0.05% to 5% nickel. The manganese preferably doesnot exceed 1%.

D.Molybdenum steels containing carbon in amounts up to 0.6% andpreferably not'over 0.4%, 0.05% to 1% molybdenum, manganese in 50amounts up to 2%, silicon in amounts up to 1%,

suitable amounts of columbium, and the remainder iron.

E. Molybdenum-nickel steels containing, in addition to the ingredientsof the molybdenum steels, 0.05% to 5% nickel. The manganese in thesesteels preferably does not exceed 1%.

F. Chromium-molybdenum steels containing carbon in amounts up to 0.6%and preferably not Usually, it will not be um, and themost useful rangeis within the I limits 0.05% to 0.25%. In general, the greater amountsof columbium should ordinarily be used in the'steels containing thegreater amounts of carbon, within the ranges specified above.

One of the most valuable properties of the columbium containing steelsof the invention is that of retaining, its normally fine grainedstructure at elevated temperatures, which property is attained" withoutdetrimentally affecting other important physical properties. v Theexpedients heretofore customarily employed to refine the grain size ofcarbon and low-alloyed steels have, in most cases, either detrimentallyaffected the toughness of the steels, or failed to prevent coarsening ofthe grain size at elevated'temperatures, during fabrication forinstance, or both.

The coarsening of the grain is considerably ag gravated in a casecarburizing process, {and in such a process the addition of columbiumtothe steel is especially advantageous, as illustrated by the data inTable I whichgives the experimentally determined grain number (A. S. T.M. Speci fication E 19-33) of the cases of a series of steels aftercarburizing for eight hours at each of three diiferent temperatures. In'each case, the grain size of the core was smaller than that of the.case.

Tabie I I v Grain No. of case after Composition of steel (remainderllOll) cumming 8 hours 7 7 Other At At At c M n S1 7 Ci) metals 925 0.975 0. 102s o.

0.16 0. 46 0. 29 None None 3 to 5 3 to 5 1 to 4 0. 15 0. 45 0.27 0.017None 3 to 8 3 to 8 2 to 8 0.17 0.48 0.26 0.45 None 7to8 5to8 5t08 0.410. 77 0.27 None None 2150 4 l to 4 1 to 4 0.38 0.80 0.27 0.06 None 5t074207 5t07 0.43 0.74 0.22 0.36 None 61:08 (H08 H08 0. 77 0. 75 0. 22 NoneNone 1 to 3 Ho 3 l to 3 0.94 0.75 0.25 0.04 None 5to7 41506 41:06 0.930.73 0.24 -0. 18 None 6t07 6to7 5to8 0.97 0. 72 0. 19 0. 41 None 5 to 85 to 8 5 to 8 0.15 1.50 0.16 None None 1 to 3 l to 3 i to 3 0.17 1.610.33 0.12 None 5t08 5t08 5to8 0.52 1.68 0.36 0.11 None M08 5to8 4to8 Ni0.16, 0.36 0.16 None 3.49 21:06 2to6 2207 0.37 0.40 0.17 None 3.52 5to93to8 2%7 0. 17 0. 47 0. 31 0; 10 3.45 6 to 9 6 to Q 5 8 0.34 0.35 0.130.08 3.40 M07 5to7 41307 0.47 0.80 0.31 0.08 342 K17 4006 4806 295659472 77 Mm 77 7mw= tmm R. A. percent El D cent The 'presence ofcolumbium substantially increases the resistance of these steels to hotox-' idation and, although the columbium steels are not to be consideredoxidation resistant in the sense that high chromium steels, forinstance, are oxidation resistant, the increase in resistance TableIII-Continued Cooled i'n airfrom 850 C'.900 C.

Composition of steel (remainder iron) rent Percent Percent PercentPercent Percent Percent 82 21 i asinnnanunmwm It will be observed fromthe data of Tables II and III that, in the steels containing up to about0.3% carbon, the addition of up to about 0.1%

columbium is increased above 0.1%, the softening will be valuable inmany uses of the steels. Table efiectof the columbium begins topredominate, V presents data illustrating this effect of columthe yieldpoint and maximum stress are decreased, and the ductility issubstantially increased.

columbium increases the yield point, maximum The ductility is onlyslightly affected. As the 25 stress. and ratio of yield point to maximumstress.

Other metals None. 0.25 to 2% Cr.

0.05 to 5% Ni, 0.25 to 2% Cr. .05 to 1% M0. .05 to 5% Ni,

Up to 1.. 0.25 to 2% Cr, 0.05 to Table VI Upto2.. U

Composition limits (remainder iron) Percom C Pergiclnt Pcrscient Up to0.6.. Up to 1..

Up to 0.6.. Up to 2..

Up to 0.6..

The invention isbased on the above-described discoveries and comprisesnew alloy steels and 0.02% to 1% columbium, substantially the limitsType of steel articles composed thereof, having in addition to Mo-NiCr-Mo.....

' of composition indicated in Table VI.

Izod impact ft.lbs., at-

Table IV Other metals As little as 0.2% columbium Composition of steel(remainder iron) cent cent cent Mn the plain carbon and low alloyedsteels con- '78 C. were cooled about an hour at 78 C. in a bath ofacetone and frozen carbon As mentioned above, the addition of columbiumTable IV contains impact data obtained in the manner described inconnection with Tables II and III, except that the samples under thehead- Per- Per- Per- Percent strength of the steels, and that theimprovement is greatest in the high carbon steels and those containingchromium.

siderably increases their impact strength at subzero temperatures.

raises the impact strength at 100 C. to 10 foot 4 pounds or more.

ing

heading 100 C. were cooled about an hour at -l00 C. in liquid propanewhich in turn was cooled with liquid air, before testing. After cooling,the specimens were rapidly transferred from the cooling medium to theIzod machine and tested. The time required for the transfer and test wasin all cases less than ten seconds.

. dioxide before testing; and the samples under the The articles of theinvention include articles deep-drawn from the steel of the invention;articles having a core containing less than 0.5%

carbon and a carburized case containing more than 0.8% carbon, and 0.02%to 1% columbium throughout. the remainder of the composition being asshown in Table VI; parts of machines and of other apparatus, required towithstand stress at moderately elevated temperatures; articles, composedoi the steel or the invention, designed for use to resist impact shockat subzero temperatures; and pressure vessels, composed of the steelofthe invention, designed to withstand two or three dimensional stressat subzero temperatures.

It will be appreciated that the specific examples herein are given byway oi! illustration, and that the invention is not limited to or bysuch examples.

We claim:

1. Low alloyed steel containing carbon in an amount not exceeding 0.6%;manganese in an amount not exceeding 2%; silicon in an amount notexceeding 1%; a substantial amount of at least one carbide forming metalof the group consisting of chromium and molybdenum, thechromium beingless than 2% and the molybdenum not exceeding 1%; 0.02% to 0.5%columbium which imparts to said steel a fine-grained structure whichpersists at all temperatures up to and somewhat above the criticalrange, increased ductility, increased impact strength at normal andsubzero temperatures, improved hot and cold workability, and increasedresistance to hot and cold oxidation, but does not impart substantialage hardening properties; and the remainder iron.

2. Steel containing carbon in an amount not exceeding 0.6%, manganese inan amount not exceeding 2%, silicon in an amount not exceeding 1%, 0.25%to less than 2% chromium, 0.02% to 0.5% columbium which imparts to saidsteel a fine-grained structure which persists at all temperatures up toand somewhat above the critical range, increased ductility, increasedimpact strength at normal and subzero temperatures, improved hot andcold workability, and increased resistance to hot and cold oxidation,but does not impart substantial age hardening properties, the remainderiron. I

3. Steel containing carbon in an amount not exceeding 0.6%, manganese inan amount not exceeding 2%, silicon in an amount not exceeding 1%, 0.05%to 1% molybdenum, 0.02% .to 0.5% columbium, the remainder iron.

4. Steel containing carbon in an amount not exceeding 0.6%, manganese inan amount not exceeding 2%, silicon in an amount not over 1%, 0.05% to1% molybdenum, 0.25% to less than 2% chromium, 0.02% to 0.5% columbium,the remainder iron.

5. Case carburized article having a .core containing less than 0.5%carbon and a carburized case containing more than 0.8% carbon, the coreand case being composed of steel containing, aside from carbon,manganese in an amount not exceeding 2%; siliconin an amount notexceeding 1%; a substantial amount of at least one carbide forming metalof the group consisting of chromium and molybdenum, the chromium beingless than 2% and the molybdenum not exceeding 1%; 0.02% to 0.5%columbium which imparts to said carburized article a fine-grainedstructure, increased ductility, and increased impact strength at normaland subzero temperatures; and the remainder iron.

I 6. Article used to resist, at subzero temperatures, impact shock ormultidimensional stress, which article is composed of a low alloyedsteel containing carbon in an amount not exceeding 0.6%; manganese in anamount not exceeding 2%; silicon in an amount not exceeding 1%; asubstantial amount of at least one carbide forming metal of the groupconsisting of chromium and molybdenum, the chromium being less than 2%and the molybdenum not exceeding 1%; 0.02% to 0.5% columbium whichimparts to said article increased impact strength at subzerotemperatures; and the remainder iron.

7. Machine element subject to impact stress at elevated temperaturesbelow 500 C. and composed of a low alloyed steel containing carbon in anamount not exceeding 0.6%; manganese in an amount not exceeding 2%;silicon in an amount not exceeding 1%; a substantial amount of at leastone carbide forming metal of the group consisting of chromium andmolybdenum,

the chromium being less than 2% and the molybdenum not exceeding 1%;0.02% to 0.5% cclumbium which imparts to. said element a. persistentfine-grainedstructure, increased ductility, and increased impactstrength at working temperatures, remainder iron.

FREDERICK M. BECKET. RUSSELL FRANKS.

